(CNN) — An “America’s Got Talent” contestant’s emotional story of getting hit by a grenade in Afghanistan is not backed up by military records. And now, questions surround whether he embellished his heroic tale.

Timothy Poe wowed the three judges on the NBC program Monday night after stuttering when he spoke, but singing “If Tomorrow Never Comes” without a hitch.

He said that the stutter was caused by the grenade attack and that he didn’t really know he could sing until his speech pathologist told him to try singing in the shower.

After receiving an emphatic “yes” from each judge, advancing him to the contest’s next round, Poe walked offstage and told host Nick Cannon, “Oh my God, it’s amazing. I was so scared up there I c-couldn’t remember where to put my fingers. I was like, oh I didn’t know.”

“I don’t know if you just noticed,” Cannon responded, congratulating him, “but this whole sentence that you just said you didn’t stutter one bit.”

In an interview Tuesday with the “You Served” podcast, Poe said he does not stutter always, “just when I get stressed or nervous or something big happens.”

On the NBC show, Poe said he served in the military for 14 years. In 2009 in Afghanistan, he said, he was struck by rocket-propelled grenade. “By the time I turned and went to jump on top of my guys, I yelled ‘grenade’ and the blast had hit me,” he said.

The attack “broke my back and gave me a brain injury, so that’s the reason why I stutter a little bit,” he said.

The Minnesota Army National Guard issued a statement saying Poe served from 2002 to 2011.

“His military records indicate that he served with the Minnesota National Guard in Kosovo from Oct. 10, 2007 until July 15, 2008, and was deployed to Afghanistan from July 28, 2009 to Aug. 30, 2009,” the statement said.

“Sgt. Poe’s official military records do not indicate that he was injured by a grenade in combat while serving in Afghanistan in 2009, as he reports. The Minnesota National Guard can also confirm that he was not awarded the Purple Heart Medal for wounds sustained in combat.”

Poe could not be reached for comment Thursday.

In his Tuesday interview, Poe said he had requested to have his medical records changed to note everything that had happened to him. The Minnesota National Guard said it has no proof that his injuries resulted from combat action, but that it would correct his records if Poe provided that proof.

He told TMZ on Wednesday that his story is true, and that not all military injuries are recorded. But he did not provide any documents to back up his story, saying he couldn’t for legal reasons, TMZ reported.

NBC did not immediately respond to a request for comment Thursday morning.

One of the three judges, radio personality Howard Stern, tweeted Wednesday that if the reports were true, he’s “disgusted,” but added that he is reserving judgment until all the facts are in.

Some people who say they served with Poe are slamming him online, insisting his story is false.

Among them is Joshua Hansen, who posted on Facebook that he was Poe’s squad leader.

“He was nowhere near direct enemy contact,” Hansen wrote. He added, “I knew where and what my guys were doing at all times … I wish he would just end this now and quit the bs and man up.”

Hansen could not be reached immediately for comment Thursday.

Lt. Col. Kevin Olson, a spokesman for the Minnesota National Guard, confirmed to CNN that Hansen and two others who are denying Poe’s story online were deployed with him in the 114th Transportation Company to Afghanistan in 2009.

Poe’s ex-wife Kelly Ballard told the New York Post that she never heard her former husband stutter and that he had no combat injuries.

For his “America’s Got Talent” performance, Poe was accompanied by his fiancee. And he talked about the moments after the grenade attack.

“When I was lying there, I thought I was never going to be able to see my daughter walk down the aisle, throw the baseball with my son again, or be able to hold them and see them,” he said.

In his interview with the “You Served” podcast Tuesday, Poe said the grenade attack “may not have happened exactly how I explained because I don’t remember a whole bunch, but the unit was there.”

He confirmed that Hansen was his squad leader.

“(Hansen) wasn’t right there when it happened, but I mean the whole unit was doing things,” Poe said.

“When (the grenade) went off, I was fine,” he added.

“I didn’t say a word about it because the dizziness had gone away for about three days or four days,” Poe said.

He said he was sent out of Afghanistan to get medical treatment in Germany for a traumatic brain injury, “because I had a blast by my head,” which caused him to forget things, “and I couldn’t walk straight.”

Poe said he has a previous, permanent back injury stemming from service in 2003 in Iraq.

When asked whether there was anything he said on the show that was inaccurate or embellished, he responded, “Sure. Just like you’re telling your kid that you were this really cool, cool person one time. It was a show, you know? It wasn’t out there to make anyone feel bad. It wasn’t out there to make the soldiers that are going through things feel bad, it was just to show them that it doesn’t matter what happens in life, you can overcome it.”